Bedrock Base Map Location 7
The light and dark banded specimens seen here are a high-grade metamorphic rock called gneiss (pronounced “nice”). Gneiss forms when pre-existing rocks are buried deep within the Earth and are subjected to extremely high temperature and pressure. This causes the parent rock to recrystallize and separate into light and dark bands of needle and plate-shaped minerals. The Huntsville Gneiss was originally deeply buried bedrock of a Himalayan-sized mountain range called the Grenville Mountains, which formed roughly 1 billion years ago as the result of continental collision along eastern North America. Over time, these mountains eroded down to the Huntsville Gneiss you see here today, which were once found some 20 miles beneath the Earth.
Huntsville, Ontario | Mesoproterozoic | 1.0 billion years old